题目内容
已知向量
(其中
为坐标原点),
则向量
与
夹角的取值范围为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231842542171732.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254232300.png)
则向量
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254248403.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254264388.png)
A.![]() | B.![]() | C.![]() | D.![]() |
D
利用CA是常数,判断出A的轨迹为圆,作出A的轨迹;数形结合求出两个向量的夹角范围.
解:
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231842545136706.png)
|
|=
,∴A点在以C为圆心,
为半径的圆上,
当OA与圆相切时对应的位置是OA 与OB所成的角最大和最小的位置
OC与x轴所成的角为
;与切线所成的为
所以两个向量所成的最小值为
-
=
;最大值为
-
=![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184255028551.png)
故选D
解:
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231842545136706.png)
|
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254607399.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254622344.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254622344.png)
当OA与圆相切时对应的位置是OA 与OB所成的角最大和最小的位置
OC与x轴所成的角为
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254654428.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254669420.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254654428.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254669420.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254903501.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254654428.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184254669420.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823184255028551.png)
故选D
![](http://thumb2018.1010pic.com/images/loading.gif)
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